Why did MB delete manual idle control on 617?
 

Was it just to make the car seem more modern and appealing to the uninformed driver? It wasn't an NA/Turbo change since the 116's with the 617 turbos still had manual idle control.

i'm guessing that there was a change to the idle governor inside the injection pump which made the external control unnecessary. did the transition occur at the same time they went from ADA to ALDA pressure sensing devices?

I don't think so. I'm pretty sure the 116 turbos had an alda.

FWIW The IPs changed to vacuum fast idle long after W123 production ceased.
However the 616 and 617 were still sold in vehicles into the 1990s, I don't know if they had the idle knobs or not though!

I think it's because most people broke the knobs off them...it's difficult to turn the knob when the throttle is in the normal idle position.

It's more accurately a pre-start-of-engine idle adjustment knob.
With the car off, you step on the accelerator pedal to move the throttle linkage, taking strain off the bowden cable...then you turn the idle adjustment knob to shorten the bowden cable...thus enriching the idle when you finally start the car.

You couldn't speed up the idle with the knob while the car was already running...unless you simultaneously feathered the accelerator pedal just the right amount.

It wasn't a "fool"-proof system.:eek:
And..who reads the instruction manual anyway?:rolleyes::)

I never knew all that! The knob on my 1978 car just freewheels, and I never bother to fix it or even investigate it further. In my defense, I do not have an owners manual for this car, although perhaps I should get one, if it explains things like that. :)

It is hard to say what motivates Mercedes to do stuff. However, the dash does look cleaner without the knob.


I have not seen any Diesel Vehicle that has such an idle control device on it except possible Boats. Other Diesel Cars don't seem to have them and don't appear to need them.


My Volvo had a thermostatically controlled gizmo for cold starting connected to the coolant.

My Fuso has a manual idle speed control. So did the CAT 3208 in my Wanderlodge.

I imagine they got rid of it because it was a cost to include for a device that was widely misunderstood and used wrongly or not at all.;)

I'm wondering if USA regs changed and prohibited hand throttle on a car. ( as in it being used as cruise control, if it goes that high )

It won't go that high, its just a manual fast idle.

The merc ones did if you had it set up right (or wrong, lol)
The old Mitsi/ Fuso Canter I used to drive had one, same with D21 Navara, etc